Document PBDRY and SLEEPQ_STOP_ON_BDRY.

Requested and reviewed by:	attilio
MFC after:	3 days

share/man/man9/sleep.9

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 4, 2008
+.Dd December 12, 2009
 .Os
 .Dt SLEEP 9
 .Sh NAME
@@ -97,6 +97,7 @@ when it resumes.
 should never be used, as it is for compatibility only.
 A new priority of 0 means to use the thread's current priority when
 it is made runnable again.
+.Pp
 If
 .Fa priority
 includes the
@@ -113,6 +114,17 @@ possible, and
 is returned if the system call should be interrupted by the signal
 (return
 .Er EINTR ) .
+If
+.Dv PBDRY
+flag is specified in addition to
+.Dv PCATCH ,
+then the sleeping thread is not stopped while sleeping upon delivery of
+.Dv SIGSTOP
+or other stop action.
+Instead, it is waken up, assuming that stop occurs on reaching a stop
+point when returning to usermode.
+The flag should be used when sleeping thread owns resources, for instance
+vnode locks, that should be freed timely.
 .Pp
 The parameter
 .Fa wmesg

share/man/man9/sleepqueue.9

@@ -23,7 +23,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 11, 2009
+.Dd December 12, 2009
 .Dt SLEEPQUEUE 9
 .Os
 .Sh NAME
@@ -198,12 +198,19 @@ A sleep queue used to implement
 .Xr pause 9 .
 .El
 .Pp
-There is currently only one optional flag:
+There are currently two optional flag:
 .Pp
 .Bl -tag -width ".Dv SLEEPQ_INTERRUPTIBLE" -compact
 .It Dv SLEEPQ_INTERRUPTIBLE
 The current thread is entering an interruptible sleep.
 .El
+.Bl -tag -width ".Dv SLEEPQ_STOP_ON_BDRY" -compact
+.It Dv SLEEPQ_STOP_ON_BDRY
+When thread is entering an interruptible sleep, do not stop it upon
+arrival of stop action, like
+.Dv SIGSTOP .
+Wake it up instead.
+.El
 .Pp
 A timeout on the sleep may be specified by calling
 .Fn sleepq_set_timeout